Hello! Thanks for the feedback and question.
Glad to hear that you enjoy the application!
I hope to add support for soundfonts in a future update, but it is a rather large addition. A possible alternative would be to add support for external Midi synthesizers or even plugins that can be configured to use a certain soundfont. I have done that before with VST and it is a lot easier than adding support for reading and playback of soundfonts.